Pre-cursor to sea monkeys or a knock-off of sea monkeys? Either way, this ad makes dinky little brine fish look like pretty darn adorable pets. You can see this ad and other vintage comic book ads here.
P.S. Random factoid: The guy who invented the Sea Monkeys toy/kit also invented the equally classic x-ray glasses (X-Ray Specs) and other "genius" products. If you've wanted to know way more than any human should know about Sea Monkeys and the guy who productized them, check out this article.